Purification of m-phenylenediamine



United States-PatentO 2,946,822 is PURIFICATION OF M-PHENYLENEDIAMI'NELeslie M. Schenck, Westfield, and Dennis L. Deutsch,

Cranford, N.J., assignors to General Aniline & Film Corporation, NewYork,'N.Y., a corporation of Delaware 7 No Drawing. Filed Oct. 5, 1956,Ser. No. 614,047 '6 Claims. "(CL 26(l- -582) This invention relates to anew and improved method for purifying m-phenylenediamine, and isparticularly .concerned with an improved method of separating.m-phenylenediamine from traces of the isomeric oand diamine with a saltor acid containing a chromate, or

dichromate anion; for example, sodium chromate or sodium bichromate, ora compound which -reacts-with water to form such anions, such aschromium oxide; and removing any precipitate that may form, either byfiltration, centrifuging; or the precipitate, if heatstable, may be leftbehind on the distillation of'the m-phenylenediamine. Them-phenylenediamine thusobtained is essentially free of or p-isomers, ortheir by-products, and, after distillation, yields apracticallycolorless product stable' to heat, light and air, and of goodpurity.

While m-phenylenediamine, contaminated by some of the oand p-isomers,when freshly distilled is SllbSlELH', tially colorless, itdarkens'rapidly on'exposure to air,"

-heat or light, and, ultimately, becomes tarry. In addition to thereduced stability to-air,- heat and light, the presence of oandp-isomers in m-phenyl'enediamine in- 2,946,822 Patented July 26 1960 iceAccordingly, the most' practical method heretofore available forproducing pure ;m-pheny1enedi'amine has been to employ an extremely puremdinitrobenzene. However, the preparation of m-dinitrobenzenq which-isuncontaminated by the oand p-dinitrobenzen'e is,itself, quite diflicult.The dinitrobenzene is normally prepared by the nitration ofnitrobe'nzene, and its preparation is well knOWn in the art, suitablemethodsfor the prepara' tion of dinitrobenzene being described,Iforlexamplq in the following references: BIOS.11'4'4; 131081986; pages117; PB. 25, 263; Fierz-Davidand .Blangey, FFunda mental Processes ofDye Chemistry,..1'949 (page-1'11).

Nitration of nitrobenzene, Iin'accordance with these known processes,always yields,in addition tom-dinitrobenzene, 5-15% of orthoand paraisomersthe quantity which gives good yields of dyes and is, furthermore,stable to air, heat and light. For this reason, 'theacceleratedreactivity of oand.pedinitrobenzene;'in irespect to iii-dinitrobenzene,is the basis of- .the commercial methods of purifying crudem-dinitrobenzene; The -most common of these purification methods isthe'reactionofa ,crude m-dinitrobenzenewith .qsodijurn sulfite or sodiumbisulfite and caustic, soda. By-thisope'ration, the bulk of the oandp-isomers is converted to the nitrosulfonic acids, and, then, throughreduction, to the. aminosulfonic acids which are water-solublecompoundsyand. canaconsequently by easily removed3(BIOS 1 1144;BIQS'1986,

page 117; PB. 25623;, page 346; Fierz-David and Blangey, FundamentalProcesses of Dye Chemistry, 1949, page 112). Other'methods include thereaction with caustic soda or sodium alcoholates, yielding thecorresponding phenol, anisol/or phenetol derivatives. The solidificationpoint of'the' dinitrobenzene, as obtained from the nitration is usually81-82 C. By purifying,

using one of the above methods, the solidification point (S.P.) can beincreased, to 89, 9 0f" c. (M.P. 90.7-91.4" 0, loc. cit.). To attainthis higher degree of purity, a more energetic reactionwithsodiums'ulfite, caustic soda, oralcoholates is required-at aprohibitive expen'se terfere with many uses of the m-phenylenediamine.Thus, the oand p-isomers, because of their strong reducing action, causedecomposition of diazonium compounds. -Hence, if impurem-phenylenediamine is used asa component for azo dyes, persistentfoaming is encountered in the coupling reaction because ofjthegeneration of nitro;,

gen. Furthermore, the decomposition products of the diazonium compounds,contaminate the dye and lower yields are obtained. There'may be cited,as a 'primeyexample of this observation; the manufacture o'f'iDianilBrown, 3 CNpand Direct Black EW, as described by Fierz-David andBlangey, "-Fundamental .Processes' of Dye Chemistry, 1949, pages 28810,292.

Heretofore, m-phenylenediamine, once prepared, could be separated fromits isomers. only withgreat difficulty,

C. (Lange Handbook of Chemistry, 1946, Handbook. Publishers, Inc.,Sandusky, Ohio). It is well known to the art that each of the isomers:can bepurified by recrystallizing the correspondingmineral acid salts,in

. cluding the hydrochloride, sulfate or nitrate. This method :is of too,great an expenseto appeal to commercial manu; facture (Org. Synthesis'Cd.,, vol. 11,112,502); .j V

. completeness, the following refere rices todetailed'specific in yieldof the desired na -dinitrobenzene,- since m-dinitrobenzene also reactswith any of theabove" reagents, but at a much slower. rate. For" thisreasongconimercial manufacture is limited to 88 90 C. S. P.--material.

Consequently, it is not commercially economical to"producemi-dinitrobenzeneof the extreme purity necessary-to give, uponreduction, Ia pure' and stable ni-pheiiylenediamine.

It is, therefore, theprimary object of the-present invention to provide.a me'thodot purifying m-phenylenediamine obtained by reductionof-rn-dinitroben'zene of a practical commercial degree o'f purity;suchas the '8i 3 to 89 C. Si; material, mentionedabove, which still'contains,'however, somelof the o antl p-isom'ers. 3 w 3 The presentinvention is directed to? the purification of m-phenylenediamine,rather-than the preparation o'fthe m-phenylenediamine, per se.""Ihemethod s known irithe art for the reduction of m-dinitrobenzeneto"m-p he1iylene- .diamine may :be used,'and suitable specificmethods'ifor its preparation have'been. described. For -thesakeofprocedures for its preparation arecited: P.B. 7036 ,page

6689; A. W. Hoifmann, Procadtoyal Soc. London-111E521, 12, 639; Schultz,Die Che'miedes steinkohlenteersf4th edition, volume I, page. 198;Pomeranz, G21 2:69;"542; Micewiez, Roc'zinki, Chem. 8,- 50; -l-fierzDavidi and Blangey, Fundamental Processespf Dye jCh'emistry, 1949, (page1-15),-and detailed-descriptionof a typical I process isgiveninFierz-David and Blangeys book (loc.

cit). According to this process, m-dinitrobenzene is reduced with ironborings and dilute hydrochloric acid at temperatures of 95-100 C. Otherprocesses use sulfuric acid, acetic" acid or otheracidic'materialswell'known to the art This type of reduction techniqueis commonly .referred to as the Bechamp method. Furthermore,mph'enylenediamine can be prepared by catalytic reduction ofthevprecursory dinitro compound, as well as by zinc reduction and/orvarious reductions known to the art.

The chemical behavior of the three'isomeric phenylenediamines is wellknown to the art. It is reported that ophenylenediamine will formaddition compounds with metal salts, including AgNO (Willstater,Pfannenstiel,

and CoClg (Hieber, Schlieszmann, Ries, Z. Anorg( Chem. .180, 100, 101,226, 227,228); ZnBr (Wahl, Centr. I,

- 1929,.1'432); znr, (Hieber, 'Appel. Z. Anorg. Chem. 196,

SnCL; (Hieber, Appel. Ann. 444, 262);

.-H [Fe(CN) (Cumming, J. Chem. Soc. 123, 2463), and

NiCl (FeigL-Furth, Monatsh. 48, 446).

' It is further disclosed that when nitrosoalkyldialkylanis- .idine,- ortoluidines, are reduced by zinc in hydrochloric acid solution, or whenaqueous solutions of mercury, zinc or cadmium salts are added tosolutions of diamines, sparsingly soluble compounds are formed (ImperialChem. Ltd.

and A. Riley, British Patent 297,989, October 17, 1927).

There is also reported that phenylenediamines and salts ofcobalt, nickeland copper form amines (R. Cernatescu et al., Ann. Sci. Univ. Jassy 18,385-403 (1933)), loc.

cit., 18, 404-414 (1933); 10c. cit., 20, 154-172 (1934)).

1 Hieber and (Z. Anorg. Allgem. Chem. 180, 105- 109 (1929)), postulatethe following structural formula is obtained when oandp-phenylenediamine are treated with zinc, cadmium andcobalt salts:

Hieber and Ries state the metal compounds formed with p-phenylenediamineexhibit greater stability than those of the ortho-isomer.

In a study of the stereochemistry of zinc, cadmium and copper (Wahl,III, Nord. Kemistmotet, 172-6, 1928, Centr. 1929, I, p. 1432), it isdisclosed that the complexes of o-, mand p-phenylenediamine with thesemetals exist neutral aqueous solutions as stable, slightly solublecompounds. Hieber and Wagener (Ann. 444, 256-65),

report a study of compound formation between diamines and tin halides.Likewise, a study of the complex compounds of cobalt andphenylenediamines has been re- I ported (Chem. Zentr. I, 609 (1926)).The use of copper sulfate in connection with analytical determinationsof phenylenediamines is described by Kulberg (Zhur. Anal.

1 'similarreaction conditions precipitate by the addition of coppersulfate; and the claim of Wahl (10c. cit.) that he I, obtained with zincor cadmium bromide, or copper salts,

precipitates with all three isomeric phenylenediamines, which arevery'slightly soluble and stable; it would seem obvious, for example,that if a mixture of mand p-phenylenediamine is treated with, say,copper sulfate, that both compounds will form .stable complexes orprecipitates. L. Asa result, part of the m-phenylenediamine, insolution, Q IG berernoved as a. metallic complex; Likewise, it

4 would be anticipated from the teachings of the literature thattreatment of a mixture containing mand o-phenylenediamine, or a mixtureof the three isomeric phenylenediamines, with salts of heavy metals,would behave in a similar manner.

While the formation of complexes of various isomeric phenylenediamines,with heavy metals, is known in the art, it will be noted that thecomplexes are formed with the cation of heavy metal salts. Surprisingly,we have discovered that compounds containing a chromium containinganion, such as sodium bichromate, will also form an insoluble complexwith phenylenediamines. Thus, when an aqueous solution of sodiumbichromate is added to an aqueous solution of p-phenylenediamine, achromate complex of the p-phenylenediamine is formed instantaneously,even at room temperature, and precipitates. when the same thing is donewith the o-isomer, a complex and resultant precipitate is formed onlyslightly slower, but still almost instantaneously. However, when anaqueous solution of sodium bichromate is added to an aqueous solution ofm-phenylenediamine, an insoluble complex is formed only when the mixtureis stored for a long time, at room temperature; or somewhat morerapidly, but still quite slowly when compared with the complex of thepand o-isomers, at elevated temperatures up to about 100 C. p

Thus, by adding a compound containing a chromate anion, e.g., sodiumbichromate or sodium chromate, to a mixture of 0-, mandp-phenylenediamines, it is possible to form addition compounds, orcomplexes with the chromate anions of the o-, and p-phenylenediamine ina manner unknown and unexpected in the art; and to remove thesecomplexes from the m-phenylenediamine before any appreciable amount ofthe chromate complex of the m-phenylenediamine is formed. Thus, it isapparent that we have discovered a very practical and economical methodfor removing oand p-phenylenediamine contaminants fromm-phenylenediamine, which, as disclosed in previous literature citationscause much difficulty in storage and consumption of them-phenylenediamine in the chemical industry. The solidification point ofthe V m-phenylenediamine, as obtained by our process, is about 63.45 C.(the melting point, which is usually about 0.5 C. higher than thesolidification point, has previously been reported to be 628 0).Investigation in our laboratory has disclosed that the reaction of thechromate anion with the oand/or p-phenylenediamine is not due to anoxidation process, as might be expected in view of the oxidizing actionof potassium permanganate on phenylenediamines under similar conditions(J. Applied Chem. U.S.S.R. 9, 846 (1936)), since potentiometrictitrations of standard solutions did not indicate a redox potential.

' e.g., a product having a solidification point of 8889 C by theconventional Bechamp, or any other standard, re-

It is highly probable that the phenomenon observed with the chromateanion is comparable to those previously reported with certain metalcations. However, it is particularly surprising, since similarformations of insoluble complexes are not observed when a compoundhaving a chromium cation is added to phenylenediamines; e.g.,

no noticeable insoluble precipitate is formed when chromic acetate, orchromic chloride, is added to any of the phenylenediamines. i

In brief, therefore, our invention .consists in the reduction ofcommercial grade of m-dinitrobenzene containing appreciable amounts ofoand pdinitrobenzene;

' duction method; and, thereafter, treating'the resultantm-phenylenedia'mine (which, however, contains appreciable amounts ofoand p-phenylenediamine) with a compound having a chromate anione.g.,chromic' acid sodium or potassium bichromate or chromate, and any 1precipitate which :may form is then removed from the m-phenylenediamine,preferably, by filtration or centriq fuging, although, if the complex isheat-stable, it may be left behind on distillation -of them-phenylenediamine.

seahorses The m-phenylenediamine Ethus obtainedzis"essentiallyitree 70fthe and p-isomers :and their by produets; and, after distillation,yields, a practically vcolorless product,- --.stable to heat,light andhours 210 g. m-dinit-robenzene, having-ans]; of -88-89 V Examp 'l No ili i Into a2-liter steel kettle was-charged-1,250:cc;iwater,

375 g. iron borings and 25 cci 20"B. hydrochloric acid.

Heat to 95-97 C.-and, while. agitating fast, :add in'- 6-'-7 C. When allin, hold at-9 6-981C. for il hour longer. 'I hen cool to 85 C. and-addslowly g. sodaash-until the mixture is slightly alkaline, and there isno more soluble iron present in the solution. Filter :hot. "Add to thefiltrate at 6540? -C. .2 0 -g. sodium'bichromate and hold at thistemperature for /z -hour longerf Filterihot. Wash the cake with somewarmwater. Thereaftergdistill off the water and distill the crude product invacuum The yield is 143.6 g. or 8'4.2% of theory. S.P.'of material63.15C.

Example No. 2

'Into a 2-liter steel kettlewas-charged 1,250fcc.*water, 375 g. ironborings and 25' cc. "BQhydrochloric-acid.

Heat to 9 5-97 C. and, while 'agitat-ing .fast, add in-G-T hours 210 g.m dinitrobenzene, having an S.P.'of '8'889 C. When all in, hold at 96-98C. for 1 hour longer. Then cool to 85 C. ,andfadd slowly 15 g. -soda*ash until the mixture is slightly alkaline andthere is no more v solubleiron present in the solution. Filter hot. "'Coo1*- to room temperature.Themadd to the cooled filtrate76 grams sodium bichromate andstir for V2hour at room temperature. Then, in order toremove anypossible-excess of'bichromate, add 12 grams of barium hydroxide crystals. v

Stir 'and' filter cold (roomtemperature). Wash the filter cake, which iscomposed primarily-'of'the'chromate complexes of the oandp-phenylenediamines and-barium chromate. Thereafter, distill 'off'thewater from the 'fil- I trate, and distill the thus recoveredcrude-m-phenylene diamine under vacuum. The yield in severalexperiments, conducted as above described, varied from 121. t0

124 grams, or 90 to .95 of theory. 'Ihesolidification -for-some of the.m-phenylenediamine to form a complex; .gand, thus,.be lost at thetemperature used for distillation,

L ;and, inaddition,- extra precautions should be exercised orgothersuitable prccautions observed. I

We have, also foundsthat the residue remaining after distillatiq n ofthe-.m-phenylenediamine, if the residue 1 contains-any chromatecomplexesof phenylenediamine, is ,.=apt to be .quite diflicult to remove from,the still; while,

/ .phenylenediamines (o-andpaphenylenediamine) are .re-

if all. excess chromate, and chromate complexes of the movedwprior-todistillation, difficultiesdue to the ignition of the stillresidue arenot encountered, and any still .residue can '-be removed by merelywashing the still with water. v

I In. order; to I remove a excess chromate before distillation of them-phenylenediamine, the addition of barium hydroxide as illustrated inExample 2, is preferred.

.: However, other precipitants, sucli as barium chloride, may

be employed,'- but ;are somewhat less preferred, since sodium chloride;is formed by reaction betweenbarium chloride .andsodium bichromate; andthe salt may be corrosive to the still. When bariumhydroxide is used,

{to :remove excess chromate, itwill .be apparentthat so- .dium hydroxideis formed, and corrosion problems with steel equipment, are notencountered.

. Alternatively, lead chromate is quite insoluble, and, thus, a:leadsaltrnay be added to remove excess chro- .mate,-;, if desired; butis less preferred than a barium 135 jghydroxide. Surprisingly, calciumchromate is quite soluble, -and, therefore, calcium'salts are notpreferred.

"While, for. easeof operation,it is preferred to employ ,-a filtrateobtained on reduction of m-dinitrobenzene, it

I will beapparent that, if;desired, commercial anhydrousm-phenylenediamine may be employed, and a solution of -,it, in water,preparedzand treated with .a compound 1 containing avchromateanion. Thismethod of operation is illustrated by the following examples.

point of the refined m-phenylenediamine was 63:5? C. e

From a consideration andcomparisonof Examples 1 and 2, above, it will'be apparentthat improvement of yield is obtained if the temperature, atwhich the treatment with the sodium, bichromate is effected, is aboutroom temperature. greater excess of bichromate was employed, since atthe temperature at which it was added, 85 C., some formation 'of thecomplex of m-phenylenediamine with chromate anion, took place, withresultant loss of m-phenylenediamine. Also, it will be apparent, fromExample 2, that it is preferable to remove the excess chromate byaddition of a precipitant therefor, such as barium hydroxide, althoughother precipitates, such as barium chloride, maybe used, if desired.This removal of excess chromate is desirable for several reasons.First,'it prevents formation, during distillation, of any complex, orprecipitate, between the excess chromate and mphenylenediamine, withresultant loss of m-phenylenedi-.

tures are used, is preferably removed prior to distillation 7 15Q;;grams,-of commercial m phenylenediamine are (115- Thus, in Example 1, asomewhat V Example 3 solved in 1250 cos. of water, by heating to 80 C.,and,

at this temperature, 15 grams of sodium bichromate are added withstirring, and the solution stirred for /2 hour at 80-85 C., and thenfiltered. After distilling off the water from the filtrate them-phenylenediamine is distilled under vacuum, and a stable, colorlessproduct obtained in good yield. Care should be exercised on breaking thevacuum, following distillation, to avoid ignition of the still residue.

Example 4 a stable, colorless product in good yield. The residue of them-phenylenediamine. While it is possible to remove the mphenylenediamiue from the complex of the oand p-isomers with thechromate, by distillation, such procedure is less preferable, sincethere is a tendency was easily removed from the still by washing withwater.

For ease of operation, it is preferable to employ a water-solublecompound containing a chromate, a bichromate, anion; e.g., sodiumchromate, or sodium obichromate, since the salt can readily be added toan aqueous solution of the m-phenylene diamine, and the insolubleproduct formed with the oand p-phenylenediamine, readily separated fromthe solution of the m-phenylene-' mate added is not critical, but, ofcourse, must be suflicient to react with the oand p-phenylenediaminecontained in the crude product. It will be apparent that a molar amountof chromate compound, equivalent to the and p-phenylenediamine, must beused in orderto assure complete removal of the oand'p-isomers.Preferably, a slight excess should be used. If the operation isconducted at room temperature, as is preferred, only a very slightexcess of chromate compound is required,"

since there is .essentially no formation of m-phenylenediamine chromatecomplex at room temperature. If,

however, the process is operated at a slightly elevated temperature,somewhat greater excess of chromate compounds is used, since thereis'some formation of cornplex with m-phenylenediamine at slightlyelevated temperatures, In spite of the loss of m-phenylenediamine,temperatures Within the range of 50-100 C. may be employed, since theloss of m-phenylenediamine is not too great at these temperatures, andsomewhat more concentrated solutions may be employed. Temperatures aboveabout 100 C. are, however, definitely less' preferred, since loss ofm-phenylenediamine becomes unduly great at such temperatures, and theremay be some tendency for thermal decomposition to take place.

It will also be noted that the process of the present invention can beused to purify not only m-phenylenediamine, itself, but alsom-phenylenediamines containing such substituents as halogen, hydroxy,alkoxy, alkyl (preferably lower alkyl) or aryl substituents. It willalso be apparent that the process of the present invention can 7 beemployed to purify ring homologues of m-phenylenel. The process ofrecovering meta-phenylenediamines.

from mixtures of the same with the orthoand paradiamine. The amount ofsodium chromat c or bichroisomers, which comprises adding to an aqueoussolution of amixture of said isomeric diamines, at a temperature below'about100 C., a water soluble compound having a chromium containinganion andsielectedjfrom the group consisting of chrom ic acidand thechromate and bichromate salts thereof to thereby form an additionproduct with o- :and p-phenylenediamines instantaneously .za'ndwhichprecipitates as formed, and separatingsaid precipitated additionproduct from the m-phenylenediamines 10 said compound having a chromiumcontaining anion with before any appreciable amount of addition productof said m-phenylenediamine is formed.

. 2. The process as defined in claim 1, wherein the treatment iseffected at room temperature.

3; The process of recovering m-phenylenediamine from mixtures of thesamewith the oand p-isomers which comprises adding to an aqueous solution'of mixture of said diamines, at a temperature below about 100 C., an,alkali metal ,chromate to thereby precipitate an addition product ofsaid jchrom'ateand the'o-and p-phenylenediamines instantaneously andwhich precipitates as formed, and separating said precipitated additionproduct from the solution of m-phenylenediamine before any appreciableamount of the additionproduct of said alkali metal 'chromate withm-phenylenediamine is formed;

4; Theprocess as defined in claim 3, wherein the treatment is'carriedout at room temperature. 7

5. The; process as defined in claim 3, wherein the alkali metal chromatespecified is sodium bichromate.

6. The process of recovering m-phenylenediamine from mixture of the samewith the oand p-isomers which comprises adding to an aqueous solution ofa mixture of said diamines, an alkali metal chromate to thereby forminstantaneously and precipitate an addition product of said chromate andthe oand p-phenylenediamine, thereafter adding a precipitant for anyexcess chromate, and thereafter separating said precipitated additionproduct and precipitated chromate compound from the solution ofm-phenylenediamine.

References Cited in the tile of this patent Malitzki: ChemischeZentralblatt, vol. 97, part 1, page Cernatescu et al.: A nn. Sci. Univ.Jassy 18, p. 391-414 1933 Poni: Anni. Sci. Univ. Jassy- 20, p. 154472.1934

1. THE PROCESS OF RECOVERING META-PHENYLENEDIAMINES FROM MIXTURE OF THESAME WITH THE ORTHO- AND PARAISOMERS, WHICH COMPRISES ADDING TO ANAQUEOUS SOLUTION OF A MIXTURE OF SAID ISOMERIC DIAMINES, AT ATEMPERATURE BELOW ABOUT 100*C. A WATER SOLUBLE COMPOUND HAVING ACHROMIUM CONTAINING ANION AND SELECTED FROM THE GROUP CONSISTING OFCHROMIC ACID AND THE CHROMATE AND BICHROMATE SALTS THEREOF TO THEREBYFROM AN ADDITION PRODUCT WITH O- AND P-PHENYLENDIAMINES INSTANTANEOUSLYAND WHICH PRECIPITATES AS FORMED, AND SEPARATING SAID PRECIPITATEDADDITION PRODUCT FROM THE M-PHENYLENEDIAMINES BEFORE ANY APPRECIABLEAMOUNT OF ADDITION PRODUCT OF SAID COMPOUND HAVING A CHROMIUM CONTAININGANION WITH SAID M-PHENYLENEDIAMINE IS FORMED.